The present invention relates to a silencer provided in a discharge line connected to an axial, screw type vacuum pump for suction of a gas including a condensing substance.
An axial, screw type vacuum pump has been used for many applications in various fields such as gas vacuuming, gas suction, cleaning, pneumatic conveying of powder/particle and viscous materials, etc.
In the vacuum pump for suction of a gas including an entrained substance like a solvent, the entrained substance included in the gas is delivered in a low pressure side of the vacuum pump. The entrained substance condenses to a drain in a discharge side of the vacuum pump under an atmospheric pressure. The drain partially accumulates in the vacuum pump and the remaining major part of the drain accumulates in a discharge line contiguous to a discharge outlet of the vacuum pump. An excessive amount of the accumulation in the discharge line flows backward into the vacuum pump.
The condensed drain, which is a non-compressible fluid, has caused problems such as a damage of an axial sealing of the vacuum pump, an over load condition of the vacuum pump, and seizing of a rotor of the vacuum pump due to the over load.
Thus, for handling a gas including a condensable substance, there has been provided a method for heating the condensable component up to a temperature at which the condensable substance vaporizes by means of a heater disposed around the discharge line or a method of using a drain tank positioned lower than the vacuum pump for recovering the drain.
For handling an ignitable gas, the method for heating the discharge line must eliminate a fear of an explosion accident. Therefore, the vacuum pump is positioned on a base frame to be higher than the drain tank, and a silencer provided in the discharge line is located separately from the vacuum pump. A drain accumulated in the silencer is dropped into the drain tank disposed lower than the silencer.
FIG. 3 is an illustration showing a general arrangement of a solvent recovery system having the vacuum pump, which is arranged along flow steps of a gas including a solvent. In the system, a mixing tank 1 is mounted with a motor 2 at the top thereof. The motor 2 has an output shaft coupled with a rotational shaft 4 of a mixing impeller 3. A gas including the solvent generated in the mixing tank is supplied into a condenser 6 via a delivery pipe 5. The gas is cooled by a cooling water flowing through a cooling water line 7 of the condenser 6. Thus condensed solvent flows downward through a drain pipe 8 of the condenser 6 to enter a drain recovery tank 9 disposed in a lower position.
A part of the solvent, which has not condensed in the condenser 6, is taken into a vacuum pump 12 together with the gas through a suction line 11 having a check valve 10.
The rotation of a driving motor 13 of the vacuum pump 12, which is transmitted to a rotational shaft 12a of the vacuum pump 12 via a coupling 14, compresses the gas including the solvent up to an atmospheric pressure to deliver the gas into a discharge line 15. Then, the gas passes through a silencer 16 disposed at a leading end of the discharge line 15 to be discharged into the atmosphere.
The condensed solvent accumulates in the discharge line 15 during the gas compression up to the atmospheric pressure. This brings the disadvantage that the accumulation flows backward into the vacuum pump 12 or that a back pressure arises due to the blockage of a rising pipe 15a of the discharge line 15, which may undesirably cause an over load of the vacuum pump 12.
To eliminate these disadvantages, there have been provided a drain tank 17 disposed in a position lower than the vacuum pump 12, a drain line 18 communicating the discharge line 15 with the drain tank 17, and a drain valve 19 for opening and closing the drain line 18. Thereby, the condensed solvent of the discharge line 15 has been discharged into the drain tank 17 to prevent the backward flow of the condensed solvent into the vacuum pump 12 and the back-pressure generation.
The reference numeral 20 designates a backward flow type cooler provided in the discharge line 15. Such vacuum pump 12 requires a discharge line provided with the silencer 16 for noise reduction of the gas before discharging the gas into the atmosphere and the drain tank 17 for recovering the condensed solvent accumulated in the discharge line 15. This disadvantageously requires a larger installation space for a discharge line system of the gas and increases a manufacturing/installation cost of the discharge line system.
An object of the present invention is to eliminate these disadvantages.
For achieving the object, a silencer with a drain recovery device according to the invention includes an enclosed tank, an inlet port positioned at one end of the tank, a discharge port positioned at another end of the tank, a partition plate separating an inner space of the tank into an inlet side chamber and an outlet side chamber. The partition plate is formed with an orifice communicating the separated chambers with each other. The partition plate has a lower end portion provided with a drain hole communicating with both the chambers. The inlet port is connected to a discharge line of a vacuum pump.
This configuration enables the silencer, which reduces a noise of a gas discharged into the atmosphere, to separate and recover a drain of the gas.
The tank is located at a position lower than the vacuum pump. The inlet side chamber of the tank is connected to a lower end of a drain discharge line communicating with a lower portion of a casing of the vacuum pump.
Thus configured silencer allows a noise reduction of a gas discharged into the atmosphere and enables separation/recovery of a drain of the gas discharged from the vacuum pump. The silencer also has the function of recovering a drain accumulated in the vacuum pump.
The tank may have a cooling water jacket for cooling a wall of the tank. The provision of the cooling water jacket cools a gas discharged from the vacuum pump to enhance condensation of a drain of the gas, improving separation of the drain.
Furthermore, the tank may be provided with a drain discharge line for discharging a drain accumulated in the tank and a shut-off valve for opening and closing the drain discharge line, which allows the discharge of the drain in the tank with ease.